1. Field of the Invention
The present invention relates generally to a system for transferring articles and, more particularly, to an integrated intra-bay transfer, storage, and delivery system for transferring an article between a conveyor which moves the articles along a conveyor path and a storage shelf, storing the article on the storage shelf, and delivering the article to a work station.
2. Description of Related Art
In various fields, delicate or valuable articles must be safely transported between work stations and the like without damaging or destroying the articles. Articles requiring careful handling include, but are not limited to, pharmaceuticals, medical systems, flat panel displays, computer hardware such as disc drive systems, modems and the like, and semiconductor wafers. The articles are often transported from station to station, such as a work station, by a conveyor. In many situations, the articles must be temporarily removed from the conveyor for processing. Preferably, the operation of the conveyor is not interrupted while the article is removed from the conveyor. After the processing has been completed, the articles must then be carefully returned to the conveyor for transport to the next work station.
In the field of semiconductor processing, for example, a manufacturing facility is typically organized into a plurality of bays each including several processing machines. FIG. 1 shows a known exemplary bay 8 having several processing machines 16 including, but not limited to, equipment for depositing films on the wafers, for cleaning and/or conditioning the wafers at various stages, and the like. As known in the art, the entrance of the processing machine is often provided with a load port 22 where the wafers may be automatically removed from a transport pod 12 or other container in a protected environment. A known load assembly 10 loads pod 12 on load port 22. Once pod 12 is properly positioned at load port 22, pod 12 is automatically opened and the wafers are extracted from pod 12 by robotic devices. A conveyor 14 moves pods 12 from processing machine 16 to processing machine 16. An inter-bay conveyor pods 12 between the bays, with stockers 24 transferring pods 12 between the inter-bay conveyor and conveyor 14.
With many applications, the value of the articles increases after the articles are processed at each work station. For example, integrated circuits are manufactured by forming a plurality of layers on a substrate such as a semiconductor wafer. The work stations used to form integrated circuits include machines for depositing the individual layers as well as machines for cleaning and/or conditioning the substrate at various stages. With advances in technology, integrated circuits have become increasingly complex and typically include multiple layers of intricate wiring. The size of the integrated circuits has decreased, greatly increasing the number of such devices on a single wafer. As a result of the increased complexity and decreased size of the integrated circuits, the value of the semiconductor wafer increases substantially as the wafer progresses through the various processing stages. The standard size of semiconductor wafers will increase from 200 mm to 300 mm or larger in the next few years, further increasing the number of integrated circuits which may be formed on a single wafer and therefore the value of each wafer. For articles such as semiconductor wafers, considerable care must be taken when handling the articles to reduce the risk of damaging the articles and incurring significant monetary losses. It is readily apparent that the inherent workers safety hazards and the risk of material damage when handling the articles increases as semiconductor wafer size increases.
Some articles, such as semiconductor wafers, must be retained in a clean room environment during processing to preserve the purity of the layers deposited on the wafer. The requirement of a clean room environment places additional constraints on the handling of these articles. For additional protection against contaminants, the semiconductor wafers are typically retained in a device, such as a sealed pod, as they are moved throughout the manufacturing facility to minimize any exposure to the environment outside of the processing machines. The pods are used to transport the articles along the conveyor.
The inlets of the semiconductor processing machines often include a load port for the automatic removal of the wafers from the pod in a protected environment. The load port shelf may be moved a limited distance, on the order of a couple of inches, to move the pod toward and away from a load port seal at the machine entrance. This horizontal shifting of the pod is minimal and does not serve any function in the movement of the pod to the load port or the transfer of the pod between the conveyor and load port.
As noted above, multiple processing machines are generally located in a tool bay. Often a stocker system is used to store pods before or after the pods are processed or in between processes when aped is transferred between several processing machines. A stocker is typically a large unit having a plurality of shelves on which the pods may be stored and a transport system for moving pods into, within, and out of the stocker. Accordingly, a stocker generally occupies a significant amount of bay space which might otherwise provide space for additional processing machines. Such a stocker system is also used to transfer pods from an inter-bay conveyor to an intra-bay conveyor as is shown in FIG. 1. One should appreciate that the amount of time an article spends within a stocker as well as the time it takes to transport an article to or from a stocker represents lost processing time of that article.
U.S. Pat. No. 5,980,183 to William J. Fosnight discloses an integrated intrabay buffer delivery, and stocker system which transfers and stocks wafer-carrying pods between various processing tools within a bay of a semiconductor wafer. The system disclosed by the Fosnight patent relies on a shuttle to transfer the pods between an inter-bay transport, various processing tools, and storage shelves. The processing throughput of the system disclosed by the Fosnight patent may be limited due to the bottle neck created where the shuttle transfers the pods to and from the interbay transport.
A simplified system for safely and accurately moving a transport pod or other article between a conveyor system and a work station without a stocker is desirable. An article transfer system which may be used to move and buffer the articles without significantly disrupting the continued operation of the conveyor system is also desirable.
The integrated intra-bay transfer, storage, and delivery system of the present invention overcomes the above identified limitations and provides an integrated system capable of moving articles between a conveyor system and one or more work stations, for example, a load port of a work station. In particular, the integrated system of the present invention can move articles to one or more storage or buffer stations for temporary storage of an article as it is moved between the conveyor system and a work station without affecting other articles transported by the conveyor system. Storage or buffering stations located adjacent work stations are more efficient than conventional centralized stockers located adjacent an interbay transfer because less time is wasted transporting the article to and from the centralized stocker.
The integrated system of the present invention includes a transfer assembly which transfers articles between the conveyor system and the buffer stations where the articles are stored until they are delivered to the work stations by a delivery robot which moves the articles between the buffer stations and the work stations. It should be appreciated that the transfer assembly of the present invention can also be configured to move articles directly between the conveyor system and the work stations whereby the delivery robot subsequently moves the articles between one or more work stations and one or more buffer stations.
The transfer assembly includes an integral lift mechanism and a displacement assembly for lifting a pod from the conveyor system and moving it to a storage station.
Alternatively, the transfer assembly includes a lift assembly for lifting a pod from the conveyor system and a separate slide assembly for moving the pod to a storage station.
The delivery robot includes a vertical movement mechanism and a horizontal movement mechanism. Since each article often has a standard configuration, for example, a semiconductor transport pod having a mushroom-shaped handle on top, the robot includes a robot arm adapted to engage the article. The robot arm engages the handle and transports the article between a storage station and a work station. For example, the robot arm may be used to move a transport pod to a load port of a work station thus allowing a tool of the work station to access wafers in the transport pod for integrated circuit fabrication. In one embodiment, the arm includes a C-shaped adaptation that passively fits into the handle of the article from one side. In other embodiments, the arm includes an active gripper that grips the handle from above.
It is an object of the present invention to provide an integrated system able to transfer an article from a conveyor system to one or more work stations having the ability to store or buffer articles at one or more storage stations until such time that a work station is available for delivery of the article.
It is another object of the present invention to provide an integrated system to safely move the article between the conveyor system, the storage stations, and the work stations.
It is another object of the present invention to provide an integrated system to efficiently move the article between the conveyor system, the storage stations, and the work stations.
It is another object of the present invention to provide an integrated system capable of buffering an article at any location not occupied by a work station loading or I/O zone thus rendering conventional stockers unnecessary and freeing floor space for additional work stations.